To gain insight into the synthesis mechanism of LTA-type zeolite, we attempted to apply a logistic function to the time dependence of relative crystallinity during the synthesis of LTA-type zeolite. We examined both a linear function and a logarithmic function, which showed a high correlation in the synthesis of MFI-type silicalite, as a function of time. As a result, the linear function was more suitable than the logarithmic function. Furthermore, we considered the reaction mechanism as follows: (1) the formation of a primary framework from the starting gel; (2) the formation of crystal nuclei through the reaction of multiple primary frameworks; and (3) the growth of crystals through the reaction of the formed crystal nuclei with the primary frameworks. We derived an integral-type reaction rate equation, with step (3) as the rate-determining step, and examined its correlation with experimental data. The derived integral-type reac-tion rate equation was consistent with the data obtained during the synthesis of LTA-type zeolite. We also found that the time dependence of relative crystallinity during the synthesis of seeded LTA-type zeolite could be analyzed using a logistic function with a linear function as a function of reaction time. Furthermore, the effect of adding seed crystals was to increase the rate constant of the crystal growth process, which is the rate-determining step, suggesting that crys-tal growth occurs mainly on the surface of the crystal nuclei.
We developed a method for simultaneously measuring the foam diameter and film thickness by combining the Opti-cal Fiber Probe (OFP) method with interferometric spectroscopy. This new technique integrates both the direct detec-tion of liquid films, based on gas-liquid phase detection principles, and the non-invasive measurement of film thickness using interferometric spectroscopy on a single optical fiber. In validation experiments using commercial thin film, high precision was confirmed, with a difference of less than 5% from the specified value. Subsequently, the OFP measured a single soap film. From the interference light signal obtained just before contact with the film, the thickness was esti-mated to be approximately 5 mu m. Immediately afterward, we can find a clear phase detection signal indicating the OFP's contact with the film. Finally, the OFP measured the soap films, vertically spaced in a glass tube, as a simulated foam for the applicability study. A cone-shaped sensor with polishing improved the detection accuracy of the OFP for liquid films. As a result, the simultaneous measurement of liquid films and their thickness within the simulated foam was achieved, and the distances of the films were measured with high precision, showing a difference of less than 1% from the visualized images.
Transtent behavior in solid oxide electrolysts cell (SOEC) stacks must be understood for practical system design and operation, because reaction heat, gas-side heat exchange, and temperature-dependent electrical characteristics strongly Interact under high-temperature conditions. In this study, a transient SOEC stack model was developed on MATLAB/Simulink by integrating stack current-voltage characteristics, electrochemical heat absorption/release, gas-side heat exchange, and inplane heat conduction. The model was applied to analyze stack responses to changes in electrolysts output. Transient-response analysts under power variation showed that the stack temperature changed more gradually than the cell voltage because of the stack thermal capacity, Indicating a difference in their time scales. The inlet side, where the reactant concentration was higher, was identified as a leading point of temperature change in both endo-thermic and exothermic phases, and this behavior governed the formation of transient in-plane temperature gradients. Under lowload operation, stack temperature decreased markedly. Sensible heat supply by inletgas heating was effective in maintaining the temperature, but it also altered the temperature and current-density distributions in the stack. These results indicate that stack characteristic data over a wide temperature range, particularly near the thermoneutral voltage, are important for transtent SOEC simulations. The proposed model is expected to be useful for thermal management studies and for future reltability and lifetime assessments coupled with stress analysts.
In this study, a microporous carbon electrode with polyvinyl alcohol (PVA), a hydrophilic binder, was prepared as enzyme immobilization electrodes of biofuel cells. Furthermore, the effect of PVA content on the electrode structure and its performance was evaluated based on electrochemical measurements. According to the analysis of particle-size distribution, the PVA content in the electrode slurry is preferably set more than 10wt% to improve the dispersibility of carbon particles. The authors investigated the impregnation of electrolytic solution and the reaction characteristics of the microporous carbon electrode using cyclic voltammetry. It was found that an increase in PVA content induces its coverage on the electrode surface, resulting in inhibiting the reactant supply to reaction sites. When used as enzyme-immobilized electrode of lactate biofuel cells, the addition of 15wt% PVA derives the optimum electrode performance.
